A long-standing problem in the medical profession relates to the ubiquitous hypodermic syringe, and more particularly, its safe disposal. The typical hypodermic syringe includes a cylindrical, barrel, an extension of the barrel supports a needle having a sharp point. The hypodermic syringe is usually accompanied by a cap having a shell portion and a mouth portion. When the mouth portion of the cap is engaged on the extension, the shell is positioned so as to enclose the needle. Thus the cap protects people who may be handling the hypodermic syringe from accidental stick injuries. When the hypodermic syringe is used, of course the cap is removed. After the hypodermic syringe has served its purpose, the user will typically recap the syringe. It is at this point in time that the stick injuries become most troublesome because the needle has already been used and it must be assumed is contaminated. However, it is at the same point in time that the user is typically engaged in other duties or preparing to move one to a further task and because the mouth of the cap is relatively small, it is very easy for the user to misdirect the needle and effect a stick injury, rather than recapping the needle which was what was intended. An example of a report of this problem is found in Sumner, "Needle Caps to Prevent Needle Stick Injuries", appearing in Infection Control, Vol. 6, No. 12, 1985, pp. 495 et seq. The patent literature addresses this problem. See:
______________________________________ U.S. Pat. No. Inventor ______________________________________ 4,419,090 Bennett 4,559,042 Votel 4,573,975 Frist 4,596,562 Vernon 4,610,667 Pedicano 4,623,336 Pedicano 4,629,453 Cooper 4,643,199 Jennings 4,654,034 Masters 4,659,330 Nelson ______________________________________
For one reason or another, the various solutions presented by the foregoing patents, while reducing the risk of accidental stick injuries, also carry countervailing disadvantages. Perhaps the most pertinent of the solutions presented in the literature is Votel. Votel describes the use of a disk 16 which he says can be slipped over the tube (of the cap) and be frictionally held in place.
It is an object of the present invention to improve the prior art solutions to accidental stick injuries. It is another object of the invention to provide a relatively simple, easy to use, inexpensive and effective safety device to prevent or reduce accidental stick injuries. It is another object of the present invention to provide a safety device which can be readily manufactured, is convenient to store and distribute, takes up little space, is easy to use and yet is effective to prevent accidental stick injuries.
The present invention can be viewed as an improvement of the Votel suggestion with several significant differences. Thus, in common with Votel, the safety device of the present invention comprises a disk which can slipped over the cap to be positioned for use. However, the present invention departs from Votel in a number of respects. Whereas Votel suggests that the disk be made "somewhat flexible or resilient", the present invention comprises a rigid disk, preferably of a plastic material such as polycarbonate.
Further features of the invention can be best explained by considering how the safety device is used. When a user first picks up a hypodermic syringe for use, the user will also acquire the safety device of the present invention. The safety device is in the form of a rigid disk with a central aperture. With the needle still capped, the cap will be inserted into a central aperture of the disk. The user can then remove the cap and put the hypodermic syringe to whatever use is required. When that use is completed, the user will attempt to recap the needle. The safety device must be effective even under circumstances in which the user's attention may not be wholly focused on the operation of recapping the needle. If the user misdirects the needle, so that the point of the needle does not enter the mouth of the cap, the needle will engage the surface of the disk with a force dependent on the force that the user has applied. If the disk is flexible (a la Votel), the pointed needle can actually flex the disk, travel past the disk and engage a body part of the user, resulting the very accidental stick injury which was to be avoided by the safety device. Furthermore, if the disk is not rigidly secured on the shell, even if the disk itself is rigid, the disk may be deflected, allowing the pointed needle to move past the disk, resulting in the very accidental stick injury which the safety device was designed to avoid.
In order to overcome these two problems, the present invention provides an improvement over the prior art solutions in at least two different areas. The central aperture of the disk, in according with the present invention, includes a plurality of radially projecting teeth. The form of the teeth and the material of the disk has been selected so that when the cap is inserted into the central aperture, the disk can be forced down toward the mouth of the cap and actually physically displace the material of the cap so as to become firmly seated on the cap. The firm seating of the disk on the cap prevents the disk from being deflected by the force of the needle impacting on a surface of the disk.
Furthermore, the safety device of the present invention comprises a rigid plastic disk with a central aperture (already described), a generally planar region surrounding the central aperture, and ridge means in the form of an outer annular region of the disk of increased thickness. A cross-section of the safety device in the vicinity of the ridge means exhibits an abrupt transition between the generally planar region of the disk and the outer annular region of increased thickness. The abrupt transition is designed so that if on recapping, the point of the needle engages the generally planar region of the disk, and tends to slide across the disk radially away from the cap, the point of the needle will engage the ridge means and tend to be trapped at the transition. Thus the ridge means is effective to tend to stop motion of the needle along the disk so that if the user misdirects the needle point on attempts to recap the needle, trapping the needle point at the ridge will reduce the risk of the needle being forced across the surface of the disk, past the disk and impinging in a body part of the user.
Accordingly, the invention provides a safety device comprising a rigid plastic disk having a central aperture, a generally planar region surrounding the central aperture and ridge means forming an outer annular region of increased thickness,
the central aperture including a plurality of radially projecting teeth for biting into and displacing material of the shell portion of the cap as the shell portion of the cap is inserted into the aperture and the disk is forced toward the mouth portion of the cap by a user on installing the disk on the cap, PA0 the ridge means engaging a point of the needle in order to tend to stop motion of the needle, if on an attempt to insert the needle into the mouth portion of the cap, the point of the needle is misdirected and engages a surface of the disk.
More particularly, a cross-section of the disk adjacent the ridge means has an abrupt transition between the generally planar region of the disk and the region of increased thickness so as to inhibit the point of the needle from smoothly sliding across both the generally planar region and past the ridge means.